Mako Vunipola will start at loose-head prop for England in Saturday's match against Italy, due to the unavailability of Joe Marler.

Marler has started all four of England's 2014 Six Nations matches but with his partner in labour, the 23-year-old will stay in London to be present at the birth rather than accompany the squad to Rome.

The RFU confirmed on Thursday that Vunipola will be promoted to the starting XV. With Alex Corbisiero recovering from a knee injury, England have elevated fourth-choice loose-head Matt Mullan to the bench.

"It is important that Joe is with his partner at this exciting time," head coach Stuart Lancaster said. "Family must always come first and everyone in the squad wishes them well.

"We have prepared for being without Joe and we have no doubt Mako will slot straight in and perform, as will Matt Mullan should he get an opportunity.

"Matt played in the autumn internationals. There's no problem with him, he's been involved right throughout the campaign. He's a good player to come on."